Method and system for monitoring the operation of a catalytic converter

ABSTRACT

The present disclosure concerns a method for monitoring the operation of a catalytic converter that is disposed in an exhaust system of an internal combustion engine, in particular of a motor vehicle, wherein an exhaust gas temperature upstream of the catalytic converter and an exhaust gas temperature downstream of the catalytic converter are determined. In order to improve the monitoring of such a catalytic converter regardless of the respective type of catalytic converter used, it is proposed with the present disclosure that an exhaust gas mass flow through the catalytic converter is determined, wherein it is determined whether a thermal inertia of the catalytic converter is present or absent according to the presence of a triggering event taking into account the exhaust gas temperatures and the exhaust gas mass flow.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No 102015212372.3, filed Jul. 2, 2015, the entire contents of which are hereby incorporated by reference for all purposes.

FIELD

The present disclosure relates generally to methods and system for a catalytic converter.

BACKGROUND/SUMMARY

Exhaust gases of an internal combustion engine, in particular of a gasoline engine or a diesel engine, can be treated with an exhaust aftertreatment system downstream of the internal combustion engine.

The exhaust aftertreatment system can comprise a catalytic converter, which is one example of an emission control device, that may be designed for selective catalytic reduction (SCR), with which oxides of nitrogen (NO_(X)) can be reduced to nitrogen and water. Furthermore, an exhaust aftertreatment system can comprise a NO_(X) storage catalytic converter, in which oxides of nitrogen can be temporarily stored in defined operating situations. An exhaust aftertreatment system can also comprise a diesel oxidation catalytic converter (DOC), with which carbon monoxide (CO) and hydrocarbons can be removed from the exhaust gas of a diesel engine by oxidation with the residual oxygen of the exhaust gas. Furthermore, an exhaust aftertreatment system can comprise a diesel particulate filter, with which carbon particles can be removed from the exhaust gas. An exhaust aftertreatment system can also comprise a combination of at least two of the aforementioned emission control devices.

It is desired to monitor the operation of the catalytic converter. In doing so, a predetermined minimum number of monitoring processes may be observed during the operation of the internal combustion engine. In some cases, a degradation of a catalytic converter, e.g., a device removal or a malfunction of the catalytic converter, may be detectable. In any case it is desirable to use an inexpensive sensor device for monitoring the operation of a catalytic converter.

It is known to detect a degradation of a catalytic converter by means of temperature signals upstream and downstream of the catalytic converter. This is advantageous because temperature sensors are relatively inexpensive. Temperature sensors are also often already existing parts of a catalytic converter control system.

There are systems in which the presence of a diesel oxidation catalytic converter can be monitored by the analysis of heat produced by exothermal reactions in the diesel oxidation catalytic converter during the regeneration of a diesel particulate filter. Such a regeneration is used for cleaning the diesel particulate filter and is usually carried out after driving 500 km to 800 km. Such long monitoring pauses between individual detections of the operating state can be sufficient for monitoring the operation of a diesel particulate filter or of a diesel oxidation catalytic converter. The operating state of a NO_(X) storage catalytic converter and of an SCR catalytic converter may, however, be detected and thereby monitored at significantly shorter time intervals. The detection of the operating state of a NO_(X) storage catalytic converter or of an SCR catalytic converter may meet legal requirements, the so-called “In-Use Performance Requirements” (IUPR), which define a lower limit for monitoring processes during real driving operations. The value for monitoring processes to be carried out on a NO_(X) storage catalytic converter or a SCR catalytic converter is currently IUPR=0.336 for EU6.

EP 2,098,695 discloses a method and a system for monitoring the operation of a catalytic converter that is disposed in an exhaust system of an internal combustion engine. The system comprises a temperature sensor that is disposed upstream of the catalytic converter for detecting a first exhaust gas temperature and a temperature sensor that is disposed downstream of the catalytic converter for detecting a second exhaust gas temperature. A catalyst bed temperature and a degree of emission control can be determined from the detected exhaust gas temperatures. The degree of degradation of the catalytic converter is determined therefrom.

U.S. Pat. No. 5,706,652 concerns a system for monitoring the operation of a catalytic converter that is disposed in an exhaust system of an internal combustion engine of a motor vehicle. The system comprises a temperature sensor that is disposed upstream of the catalytic converter for detecting a first exhaust gas temperature and a temperature sensor that is disposed downstream of the catalytic converter for detecting a second exhaust gas temperature. The extent of the exothermal reactions in the catalytic converter is detected by means of the detected exhaust gas temperatures. The extent of the exothermal reactions is compared with predetermined criteria in order to be able to draw conclusions regarding the state of the catalytic converter.

The present disclosure concerns a method for monitoring the operation of a catalytic converter that is disposed in an exhaust system of an internal combustion engine, in particular of a motor vehicle, wherein an exhaust gas temperature upstream of the catalytic converter and an exhaust gas temperature downstream of the catalytic converter are determined.

Furthermore, the present disclosure concerns a system for monitoring the operation of a catalytic converter that is disposed in an exhaust system of an internal combustion engine, in particular of a motor vehicle, comprising at least one temperature sensor that is disposed upstream of the catalytic converter for detecting a first exhaust gas temperature and at least one temperature sensor that is disposed downstream of the catalytic converter for detecting a second exhaust gas temperature.

It is an object of the present disclosure to monitor a catalytic converter that is disposed in an exhaust system of an internal combustion engine regardless of the respective type of catalytic converter used.

In one example, the issues described above may be addressed by a method for monitoring the operation of a catalytic converter that is disposed in an exhaust system of an internal combustion engine, in particular of a motor vehicle, an exhaust gas temperature upstream of the catalytic converter, an exhaust gas temperature downstream of the catalytic converter and an exhaust gas mass flow through the catalytic converter are determined, wherein it is determined whether a thermal inertia of the catalytic converter is present or not according to the existence of a triggering event and while taking into account the exhaust gas temperatures and the exhaust gas mass flow.

As an example, the exhaust gas mass flow through the catalytic converter can be estimated from a measured air mass flow delivered to the internal combustion engine and an injected amount of fuel. In the case of low pressure exhaust gas recirculation, an exhaust gas recirculation mass flow still has to be added if the catalytic converter sits in the exhaust gas recirculation loop. This enables the detection of the activity (e.g., presence) or the inactivity (e.g., absence) of a catalytic converter in an arbitrary operating cycle of the internal combustion engine, once the triggering event exists. In particular, by suitable selection of the triggering event such a detection can take place after a third operating cycle of the internal combustion engine. In this case the triggering event can comprise the fulfillment of one or more triggering criteria. The detection of the presence or the absence of the catalytic converter is triggered by the occurrence of the triggering event at suitable short time intervals, which enables accurate monitoring of the operation of the catalytic converter. In particular, specified requirements relating to the monitoring of the catalytic converter can be reliably met in this way. If the catalytic converter is present, its mass and hence its thermal inertia are present. If the catalytic converter is not present, its thermal inertia is also not present. Hence it can be concluded whether the catalytic converter is present or not from the presence or absence of the thermal inertia of the catalytic converter.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of an exemplary embodiment of a system according to the present disclosure in combination with an exemplary embodiment of a diesel internal combustion engine.

FIG. 2 shows a schematic representation of a further exemplary embodiment of a system according to the present disclosure in combination with a further exemplary embodiment of a diesel internal combustion engine.

FIG. 3 shows a schematic representation of an exemplary embodiment of an algorithm for the detection of a triggering event.

FIG. 4 shows a schematic representation of a further exemplary embodiment of an algorithm for the detection of a triggering event.

FIG. 5 shows a schematic representation of a part of an exemplary embodiment of an algorithm designed for performing the method according to the present disclosure.

FIG. 6 shows a schematic representation of a further part of an exemplary embodiment of an algorithm designed for performing the method according to the present disclosure.

FIG. 7 shows a graphical representation of an assessment result obtained with the method according to the present disclosure.

DETAILED DESCRIPTION

The following description relates to systems and methods for measuring exhaust gas temperatures proximal to a catalytic converter to determine a temperature of the catalytic converter. A location of the temperature sensors relative to the catalytic converter is shown in FIGS. 1 and 2. An algorithm for applying one or more filters to temperature measurements for estimating a temperature of the catalytic converter is shown in FIGS. 3, 4, 5, and 6. A graph depicting final values of the algorithm is shown in FIG. 7.

The method may be used regardless of the respective type of catalytic converter used, because in particular NO_(X) storage catalytic converters and SCR catalytic converters can also be monitored because of the short time intervals between detections of the presence or the absence of such catalytic converters with the method according to the present disclosure. With the method, however, the operation of a diesel particulate filter, of a diesel oxidation catalytic converter and similar can also be monitored, where longer time intervals between individual detections of the presence or the absence are considered to be sufficient. The catalytic converter can be disposed at any point in the exhaust system of the internal combustion engine.

The exhaust gas temperatures can be detected by means of a temperature sensor that is disposed upstream of the catalytic converter and a temperature sensor that is disposed downstream of the catalytic converter. The temperature sensor that is disposed upstream of the catalytic converter can be a specific temperature sensor for performing the method according to the present disclosure or a temperature sensor that is already present upstream on a further device of the internal combustion engine, by means of which the exhaust gas temperature upstream of the catalytic converter can be measured or estimated.

The present disclosure is based inter alia on the knowledge that a graph resulting from a time recording of the exhaust gas temperature upstream of the catalytic converter coincides with a graph resulting from a time recording of the exhaust gas temperature downstream of the catalytic converter without the presence of the catalytic converter. The graphs resulting from the time derivatives of said temperature profiles also coincide. By contrast, in the presence of the catalytic converter there is a time offset between the graphs of the exhaust gas temperatures and the graphs of the time derivatives of the exhaust gas temperature profiles. This is the case because the temperature signal of the exhaust gas temperature downstream of the catalytic converter is delayed and filtered by the mass present in the catalytic converter between the temperature sensors compared to the temperature signal of the exhaust gas temperature upstream of the catalytic converter.

The present disclosure is further based on the knowledge that the time constant of a heat exchange between the exhaust gas mass flow through the catalytic converter and the catalytic converter is proportional to the quotient of the mass of the catalytic converter and the exhaust gas mass flow. Consequently, the mass of the catalytic converter is proportional to the product of the exhaust gas mass flow and the time constant for the heat exchange. The exhaust gas mass flow through the catalytic converter can be detected or estimated according to the method according to the present disclosure, and determined thereby. According to the present disclosure, an expression can be derived from the detected exhaust gas mass flow and the detected exhaust gas temperatures, based on which expression an assessment can be carried out of whether the catalytic converter to be monitored is present or absent.

According to an advantageous embodiment, a temperature signal corresponding to the exhaust gas temperature upstream of the catalytic converter is produced and then low-pass filtered, wherein a degree of change of the low-pass filtered temperature signal is detected, wherein a magnitude of the degree of change of the low-pass filtered temperature signal is detected, low-pass filtered and then compared with a predetermined limit value, and wherein the presence of the triggering event is concluded if the low-pass filtered magnitude exceeds the predetermined limit value. The low-pass filtering of the temperature signal can be carried out using a low-pass filter of the second or a higher order. The degree of change of the low-pass filtered temperature signal is determined by means of the second time derivative of the temperature profile of the temperature signal. The low-pass filtering of the magnitude of the degree of change of the low-pass filtered temperature signal can be carried out using a low-pass filter of the first or a higher order. The comparison of the low-pass filtered magnitude of the degree of change of the low-pass filtered temperature signal with the predetermined limit value can be carried out using a comparison operator. If the low-pass filtered magnitude of the degree of change of the low-pass filtered temperature signal is greater than the predetermined limit value, it is detected whether the catalytic converter is active, e.g., present, or inactive, e.g., not present. The probability that the low-pass filtered magnitude of the degree of change of the low-pass filtered temperature signal exceeds the predetermined limit value is such that the detection of the presence or absence of the catalytic converter is carried out at relatively short time intervals during operating cycles of the internal combustion engine. Owing to the large filter constants of the low-pass filter, a separation between temperature signals into exhaust gas temperatures detected upstream of the catalytic converter and temperature signals for exhaust gas temperatures detected downstream of the catalytic converter is possible after a certain time. The temperature signals may have very minimal dynamics. In a static state the dynamics of the two temperature signals are equal, so that separation of the two temperature signals is unlikely.

According to a further advantageous embodiment, a mass flow signal corresponding to the mass flow of the exhaust gas is produced and then low-pass filtered, wherein the low-pass filtered mass flow signal is compared with a predetermined mass flow limit value, and wherein the presence of the triggering event is concluded if the low-pass filtered mass flow signal is less than the predetermined mass flow limit value. The low-pass filtering of the mass flow signal can be carried out using a low-pass filter of the first or a higher order. The comparison of the low-pass filtered mass flow signal with a predetermined mass flow limit value can be carried out using a comparison operator. If the low-pass filtered mass flow signal is less than the predetermined mass flow limit value, it is detected whether the catalytic converter is active, e.g., present, or inactive, e.g., not present. The probability that the low-pass filtered mass flow signal is less than the predetermined mass flow limit value is such that the detection of the presence or absence of the catalytic converter is carried out at relatively short time intervals during operating cycles of the internal combustion engine. The higher the exhaust gas mass flow through the catalytic converter corresponds to a shorter time delay between the temperature signals upstream and downstream of the catalytic converter.

A further advantageous embodiment provides that a first temperature signal corresponding to the exhaust gas temperature upstream of the catalytic converter is produced and then low-pass filtered, wherein a change of the low-pass filtered first temperature signal is detected, wherein a second temperature signal corresponding to the exhaust gas temperature downstream of the catalytic converter is produced and then low-pass filtered, wherein a change of the low-pass filtered second temperature signal is detected, wherein a mass flow signal corresponding to the exhaust gas mass flow is produced and is then low-pass filtered, wherein the change of the low-pass filtered second temperature signal is subtracted from the change of the low-pass filtered first temperature signal and a corresponding temperature difference signal is produced, wherein a magnitude of the temperature difference signal is detected, wherein the magnitude of the temperature difference signal is multiplied by the low-pass filtered mass flow signal and a corresponding product signal is produced, wherein the product signal is low-pass filtered, wherein a magnitude of the change of the low-pass filtered first temperature signal is detected and is low-pass filtered, wherein the low-pass filtered product signal is divided either by the low-pass filtered magnitude of the change of the low-pass filtered first temperature signal or, if the same is less than a predefined minimum value, by the minimum value and a corresponding assessment signal is produced, based on which it is determined whether the thermal inertia of the catalytic converter is present or absent. The low-pass filtering of the first temperature signal can be carried out using a low pass of the second or a higher order. The change of the low-pass filtered first temperature signal can be detected by means of the first time derivative of the profile of the first temperature signal. The low-pass filtering of the second temperature signal can be carried out using a low pass of the second or a higher order. The change of the low-pass filtered second temperature signal can be detected by means of the first time derivative of the profile of the second temperature signal. The low-pass filtering of the mass flow signal can be carried out using a low-pass filter of the first or a higher order. The low-pass filtering of the exhaust gas mass flow signal is used for the synchronization of the exhaust gas mass flow signal with the temperature signals of the temperature sensors, which are delayed in time relative to the exhaust gas mass flow signal because of the slow reaction of the temperature sensors. The subtraction of the change of the low-pass filtered second temperature signal from the change of the low-pass filtered first temperature signal and the production of a corresponding temperature difference signal can be carried out by means of a subtractor. The multiplication of the magnitude of the temperature difference signal by the low-pass filtered mass flow signal and the production of the corresponding product signal can be carried out by means of a multiplier. The low-pass filtering of the product signal can be carried out using a low-pass filter of the first or a higher order. The low-pass filtering of the magnitude of the change of the low-pass filtered first temperature signal can be carried out using a low-pass filter of the first or a higher order. The comparison of the magnitude of the low-pass filtered change of the low-pass filtered first temperature signal with the predetermined minimum value can be carried out using a minmax element. The division of the low-pass filtered product signal either by the low-pass filtered magnitude of the change of the low-pass filtered first temperature signal or by the minimum value, and the production of the corresponding assessment signal can be carried out using a divider. It has been found that the mass of the catalytic converter can be identified from the product of the exhaust gas mass flow and the expression (T_(upstream)−T_(downstream))/T_(upstream), wherein T_(upstream) is the exhaust gas temperature upstream of the catalytic converter and T_(downstream) is the exhaust gas temperature downstream of the catalytic converter. The assessment signal is a modification of said product, in order to be able to reliably assess whether the catalytic converter is active, e.g., present, or inactive, e.g., not present, using the respective product value.

A system according to the present disclosure for monitoring the operation of a catalytic converter that is disposed in an exhaust system of an internal combustion engine, in particular of a motor vehicle, comprises at least one temperature sensor that is disposed upstream of the catalytic converter for detecting a first exhaust gas temperature, at least one temperature sensor that is disposed downstream of the catalytic converter for detecting a second exhaust gas temperature, at least one device for detecting an exhaust gas mass flow through the catalytic converter and at least one electronic unit that has a signaling connection to the temperature sensors and the device and that is designed to detect whether a triggering event exists or not by taking into account the exhaust gas temperatures and the exhaust gas mass flow, and following the detection of the existence of the triggering event to determine whether thermal inertia of the catalytic converter exists or not.

The method is correspondingly associated with the system. In particular, the system may perform the method according to one of the aforementioned embodiments or any combination thereof. The device can be in the form of a sensor device for directly detecting the exhaust gas mass flow through the catalytic converter or for indirectly estimating the exhaust gas mass flow through the catalytic converter.

According to one embodiment, the electronic unit is designed to produce a temperature signal corresponding to the first exhaust gas temperature and then to subject it to low-pass filtering, to detect a degree of change of the low-pass filtered temperature signal, to detect a magnitude of the change of the low-pass filtered temperature signal, to subject it to low-pass filtering and then to compare the same with a predetermined limit value, and to conclude the presence of the triggering event if the low-pass filtered magnitude exceeds the predetermined limit value.

According to another embodiment, the electronic unit is designed to produce a mass flow-signal corresponding to the exhaust gas mass flow and then to subject said signal to low-pass filtering, to compare the low-pass filtered mass flow signal with a predetermined mass flow limit value, and to conclude the presence of the triggering event if the low-pass filtered mass flow signal is less than the predetermined mass flow limit value.

Another embodiment provides that the electronic unit is designed to produce a first temperature signal corresponding to the first exhaust gas temperature and then to subject the signal to low-pass filtering, to detect a magnitude of the change of the low-pass filtered first temperature signal, to produce a second temperature signal corresponding to the second exhaust gas temperature and then to subject said signal to low-pass filtering, to detect a magnitude of the change of the low-pass filtered second temperature signal, to produce a mass flow signal corresponding to the exhaust gas mass flow and then to subject said signal to low-pass filtering, to subtract the change of the low-pass filtered second temperature signal from the change of the low-pass filtered first temperature signal and to produce a corresponding temperature difference signal, to detect a magnitude of the temperature difference signal, to multiply the magnitude of the temperature difference signal by the low-pass filtered mass flow signal and to produce a corresponding product signal, to subject said product signal to low-pass filtering, to detect a magnitude of the detected change of the low-pass filtered first temperature signal and to subject said signal to low-pass filtering, to divide said low-pass filtered product signal either by the magnitude of the low-pass filtered change of the low-pass filtered first temperature signal, or if the same is less than a predefined minimum value, by the minimum value, and to produce a corresponding assessment signal, and based on said assessment signal to determine whether the thermal inertia of the catalytic converter exists or not.

FIG. 1 shows a schematic representation of an exemplary embodiment of a system according to the system 1 for monitoring the operation of an SCR catalytic converter 4 that is disposed in an exhaust system 2 of a diesel internal combustion engine 3 of a motor vehicle. A NO_(X) storage catalytic converter 5 and a diesel particulate filter 6 downstream thereof are also disposed in the exhaust system 2. The SCR catalytic converter 4 is located in an underfloor arrangement. There are a temperature sensor 7 upstream of the NO_(X) storage catalytic converter 5, a temperature sensor 8 downstream of the NO_(X) storage catalytic converter 5 and upstream of the diesel particulate filter 6 as well as a temperature sensor 9 downstream of the diesel particulate filter 6.

The system 1 comprises a temperature sensor 10 that is disposed in the exhaust system 2 upstream of the SCR catalytic converter 4 for detecting a first exhaust gas temperature and a temperature sensor 11 that is disposed in the exhaust system 2 downstream of the SCR catalytic converter 4 for detecting a second exhaust gas temperature. Furthermore, the system 1 comprises a device 47 for detecting an exhaust gas mass flow through the SCR catalytic converter 4 and an electronic unit 12 that has a signaling connection to the temperature sensors 10 and 11 and the device 47 and that is designed to detect whether a triggering event exists or not, and following detection of the existence of the triggering event, while taking into account the exhaust gas temperatures and the exhaust gas mass flow, to determine whether thermal inertia of the SCR catalytic converter 4 exists or not. The exhaust gas mass flow in the catalytic converter can be estimated from the measured air mass flow in the diesel internal combustion engine (AMF, air mass flow) and the injected fuel.

FIG. 2 shows a schematic representation of an exemplary embodiment of the system 1. As such, components previously described are similarly numbered in subsequent figures. The system 1 may monitor the operation of a catalytic converter 13 that is disposed in an exhaust system 2 of a diesel internal combustion engine 3 of a motor vehicle. The catalytic converter 13 is a combination of an SCR catalytic converter and a diesel particulate filter. A NO_(X) storage catalytic converter 5 is also connected immediately upstream of the catalytic converter 13. There are a temperature sensor 7 upstream of the NO_(X) storage catalytic converter 5, a temperature sensor 8 downstream of the NO_(X) storage catalytic converter 5 and upstream of the catalytic converter 13 as well as a temperature sensor 9 downstream of the catalytic converter 13.

The system 1 comprises a temperature sensor 10 that is disposed in the exhaust system 2 upstream of the catalytic converter 13 for detecting a first exhaust gas temperature and a temperature sensor 11 that is disposed in the exhaust system 2 downstream of the catalytic converter 13 for detecting a second exhaust gas temperature. Furthermore, the system comprises 1 a device 47 for detecting an exhaust gas mass flow through the catalytic converter 13 and an electronic unit 12 that has a signaling connection to the temperature sensors 10 and 11 and the device 47 and that is designed to detect whether a triggering event exists or not, and following detection of the existence of the triggering event, while taking into account the exhaust gas temperatures and the exhaust gas mass flow, to determine whether a thermal inertia of the catalytic converter 13 exists or not. The exhaust gas mass flow in the catalytic converter can be estimated from the measured air mass flow in the diesel internal combustion engine (AMF, air mass flow) and the injected fuel. FIGS. 3, 4, 5, and 6 describe a method for measuring a first temperature of exhaust gas with a first temperature sensor and a second temperature of exhaust gas with a second temperature sensor. The first temperature sensor is upstream of a catalyst and the second temperature sensor is downstream of the catalyst. Thus, the first temperature of exhaust gas is substantially equal to a temperature of exhaust gas entering the catalyst and the second temperature of exhaust gas is substantially equal to the temperature of exhaust gas exiting the catalyst. Additionally an exhaust gas mass flow is measured with an exhaust mass flow sensor integrated into the catalyst.

The method further comprises low-pass filtering the first and second temperatures with a low-pass filter of a second or higher order. The low-pass filtered first and second temperature signals are differentiated against time to determine first and second temperature change signals, respectively. The exhaust gas mass flow is low-pass filtered with a low-pass filter of a first or higher order.

The method further includes calculating a difference between the first and second temperature change signals and multiplying the difference by the low-pass filtered exhaust gas mass flow to generate a product signal. The product signal is then low-pass filtered via a low-pass filter of a first or higher order.

A change between the differentiated first temperature change signal and the low-pass filtered first temperature signal is calculated. The change is then compared to a threshold value. If the change is larger than the threshold value, then the low-pass filtered product signal is divided by the change. If the change is smaller than the threshold value, then the low-pass filtered product signal is divided by the threshold value. This creates an assessment signal. The catalyst is active when the assessment signal is greater than a threshold assessment signal (e.g., 10). The catalyst is inactive when the assessment signal is less than the threshold assessment signal. As such, engine adjustments may occur in response to the catalyst being inactive as an attempt to reduce emissions. Adjustments may include decreasing torque output, increasing exhaust gas temperature, decreasing vehicle speed, and/or other adjustments conducive toward activating the catalyst and/or reducing emissions. Adjustments for increasing the exhaust gas temperature may include retarding spark, delaying a primary injection, and/or increasing a secondary injection volume.

FIG. 3 shows a schematic representation of an exemplary embodiment of an algorithm for the detection of a triggering event. The algorithm can, for example, be implemented with an electronic unit (e.g., electronic unit 12) according to FIGS. 1 and 2. A first exhaust gas temperature upstream of a catalytic converter m be monitored is initially detected in step 48. This can be carried out by means of a separate temperature sensor or a temperature sensor that is already provided on an upstream device of the exhaust system. In step 48 a temperature signal corresponding to the first exhaust gas temperature is produced. In step 14 the temperature signal corresponding to the first exhaust gas temperature is subjected to low-pass filtering by means of a low-pass filter of the second or a higher order. The low-pass filtered temperature signal is then differentiated against time twice in step 15, whereby a degree of change of the low-pass filtered temperature signal is detected. In step 16 the magnitude of the degree of change of the low-pass filtered temperature signal is detected. In step 17 the magnitude of the degree of change of the low-pass filtered temperature signal is subjected to low-pass filtering by means of a low-pass filter of the first or a higher order. In step 18 the low-pass filtered magnitude of the degree of change of the low-pass filtered temperature signal is compared with a predetermined limit value 19 in order to conclude the presence of the triggering event if the low-pass filtered magnitude exceeds the predetermined limit value 19, whereupon a triggering signal 20 is produced.

FIG. 4 shows a schematic representation of an exemplary embodiment of an algorithm for the detection of a triggering event. The algorithm can, for example, be implemented with an electronic unit (e.g., electronic unit 12 shown in FIGS. 1 and 2). In step 21 an exhaust gas mass flow is detected and a mass flow signal corresponding to the exhaust gas mass flow is produced. In step 22 the mass flow signal is subjected to low-pass filtering by means of a low-pass filter of the first or a higher order. In step 23 the low-pass filtered mass flow signal is compared with a predetermined mass flow limit value 24 to conclude the presence of the triggering event if the low-pass filtered mass flow signal is less than the predetermined mass flow limit value 24, whereupon a triggering signal 25 is produced.

FIG. 5 shows a schematic representation of a part of an exemplary embodiment of an algorithm designed for performing the method according to the present disclosure. The algorithm can for example be implemented with an electronic unit (e.g., electronic unit 12 shown in FIGS. 1 and 2). In step 26 a first exhaust gas temperature upstream of a catalytic converter to be monitored is initially detected. This can be carried out by means of a separate temperature sensor or by a temperature sensor that is already present on an upstream device of the exhaust system. In step 26 a temperature signal 27 corresponding to the first exhaust gas temperature is produced. In parallel therewith, in step 26 a second exhaust gas temperature downstream of the catalytic converter to be monitored is detected. In step 26 a temperature signal 28 corresponding to the second exhaust gas temperature is produced. In parallel therewith, in step 26 an exhaust gas mass flow is determined and a mass flow signal 29 corresponding to the exhaust gas mass flow is produced. In step 30 the temperature signals 27 and 28 are each low-pass filtered by means of a low-pass filter 31 or 32 of the second or a higher order. In parallel therewith, the mass flow signal 29 is low-pass filtered by means of a low-pass filter 33 of the first or a higher order and a low-pass filtered mass flow signal 34 is produced thereby. In step 35 the low-pass filtered temperature signals are each differentiated once against time in order to detect a change of the low-pass filtered temperature signals and to produce a respective temperature change signal 36 or 37. The low-pass filtered mass flow signal 34 and the temperature change signals 36 and 37 are processed further according to FIG. 6.

FIG. 6 shows a schematic representation of a further part of an exemplary embodiment of an algorithm designed for performing the method according to the present disclosure. The algorithm can for example be implemented with an electronic unit (e.g., electronic unit 12 shown in FIGS. 1 and 2). In step 38 the change of the low-pass filtered second temperature signal or the temperature change signal 37 is subtracted from the change of the low-pass filtered first temperature signal or the temperature change signal 36 and a corresponding temperature difference signal is produced, the magnitude of which is detected in step 39. The magnitude of the temperature difference signal is multiplied in step 40 by the low-pass filtered mass flow signal 34 and a corresponding product signal is produced, which is subjected to low-pass filtering in step 41 by means of a low-pass filter of the first or a higher order. In step 42 the magnitude of the detected change of the low-pass filtered first temperature signal or of the temperature change signal 36 is detected. In step 43 the magnitude of the temperature change signal 36 is subjected to low-pass filtering by means of a low-pass filter of the first or a higher order. In step 44 the low-pass filtered product signal is divided either by the low-pass filtered magnitude of the change of the low-pass filtered first temperature signal or, if this is less than a predefined minimum value 45, by the minimum value 45 and a corresponding assessment signal 46 is produced, based on which it is determined whether thermal inertia of the catalytic converter is present or absent. A minmax element 49 is provided for this purpose. The values of the assessment signal 46 are significantly higher in the presence of a catalytic converter than when no catalytic converter is present. This is shown graphically in FIG. 7.

In one example, additionally or alternatively, engine operating parameters may be adjusted if the catalytic converter is not present (e.g., not lit off). As an example, a torque output may be decreased to reduce emissions expelled from the engine when the catalytic converter is unable to treat the emissions. It will be appreciated that other engine operating parameters may be adjusted to decrease engine emissions when the catalytic converter is not present.

FIG. 7 shows a graphical representation of an assessment result obtained with the method according to the present disclosure. The assessment signal D is plotted against the time t. The values of the assessment signal D that are greater than or equal to 10 are associated with a catalytic converter being present, whereas values of the assessment signal D that are less than 10 are associated with a catalytic converter not being present. A clear separation between the assessment signals associated with the catalytic converter being present and the assessment signals associated with the catalytic converter not being present is thus possible.

In this way, a catalytic converter temperature may be determined by temperature sensors located upstream and downstream of the catalytic converter. The technical effect of determining a temperature of the catalytic converter by measuring exhaust gas temperature is to calculate if the catalytic converter is present. Engine operating parameters may be adjusted based on whether the catalytic converter is present or not present.

A first method for monitoring an operation of a catalytic converter disposed in an exhaust system of an internal combustion engine of a motor vehicle, wherein an exhaust gas temperature upstream of the catalytic converter and an exhaust gas temperature downstream of the catalytic converter are determined, wherein an exhaust gas mass flow through the catalytic converter is determined, wherein it is determined whether a thermal inertia of the catalytic converter is present or absent according to a presence of a triggering event taking into account the exhaust gas temperatures and the exhaust gas mass flow. A first example of the method further includes where a temperature signal corresponding to the exhaust gas temperature upstream of the catalytic converter is determined and is then low-pass filtered, wherein a degree of change of the low-pass filtered temperature signal is detected, wherein a magnitude of the degree of change of the low-pass filtered temperature signal is detected, low-pass filtered and then compared with a predetermined limit value, and wherein the presence of the triggering event is concluded if the low-pass filtered magnitude exceeds the predetermined limit value. A second example of the method optionally including the first example further includes where a mass flow signal corresponding to the exhaust gas mass flow is produced and low-pass filtered, wherein the low-pass filtered mass flow signal is compared with a predetermined mass flow limit value, and wherein the presence of the triggering event is concluded if the low-pass filtered mass flow signal is less than the predetermined mass flow limit value. A third example of the method optionally including one or more of the first and second examples further includes where a first temperature signal corresponding to the exhaust gas temperature upstream of the catalytic converter is produced and low-pass filtered, wherein a magnitude of a degree of change of the low-pass filtered first temperature signal is detected, wherein a second temperature signal corresponding to the exhaust gas temperature downstream of the catalytic converter is produced and low-pass filtered, wherein a change of the low-pass filtered second temperature signal is detected, wherein a mass flow signal corresponding to the exhaust gas mass flow is produced and low-pass filtered, wherein the change of the low-pass filtered second temperature signal is subtracted from the change of the low-pass filtered first temperature signal and a corresponding temperature difference signal is produced, wherein a magnitude of the temperature difference signal is detected, wherein the magnitude of the temperature difference signal is multiplied by the low-pass filtered mass flow signal and a corresponding product signal is produced, wherein the product signal is low-pass filtered, wherein a magnitude of the change of the low-pass filtered first temperature signal is detected and is low-pass filtered, wherein the low-pass filtered product signal is divided either by the low-pass filtered magnitude of the change of the low-pass filtered first temperature signal or, if the same is less than a predefined minimum value, by the minimum value and a corresponding assessment signal is produced, based on which it is determined whether the thermal inertia of the catalytic converter is present or absent.

A first system for monitoring an operation of a catalytic converter disposed in an exhaust system of an internal combustion engine of a motor vehicle, comprising at least one temperature sensor that is disposed upstream of the catalytic converter for detecting a first exhaust gas temperature and at least one temperature sensor that is disposed downstream of the catalytic converter for detecting a second exhaust gas temperature, characterized by at least one device for detecting an exhaust gas mass flow through the catalytic converter and at least one electronic unit that has a signaling connection to the temperature sensors and the device and that is designed to detect whether a triggering event exists or not, and to determine whether a thermal inertia of the catalytic converter is present or absent following the detection of the existence of the triggering event while taking into account the exhaust gas temperatures and the exhaust gas mass flow. A first example of the system further includes where the electronic unit is designed to produce a temperature signal corresponding to the first exhaust gas temperature and then to subject the signal to low-pass filtering, to detect a degree of change of the low-pass filtered temperature signal, to detect a magnitude of the degree of change of the low-pass filtered temperature signal, to subject the magnitude to low-pass filtering and then to compare the low-pass filtered magnitude with a predetermined limit value, and to conclude the triggering event being present if the low-pass filtered magnitude exceeds the predetermined limit value. A second example of the system optionally including the first example further includes where the electronic unit produces a mass flow signal corresponding to the exhaust gas mass flow and subjects the signal to low-pass filtering, to compare the low-pass filtered mass flow signal with a predetermined mass flow limit value, and to determine the triggering event being present if the low-pass filtered mass flow signal is less than the predetermined mass flow limit value. A third example of the system optionally including one or more of the first and second examples further includes where the electronic unit produces a first temperature signal corresponding to the first exhaust gas temperature and then to subject the signal to low-pass filtering, to detect a change of the low-pass filtered first temperature signal, to produce a second temperature signal corresponding to the second exhaust gas temperature and then to subject the signal to low-pass filtering, to detect a change of the low-pass filtered second temperature signal, to produce a mass flow signal corresponding to the exhaust gas mass flow and then to subject the signal to low-pass filtering, to subtract the change of the low-pass filtered second temperature signal from the change of the low-pass filtered first temperature signal and to produce a corresponding temperature difference signal, to detect a magnitude of the temperature difference signal, to multiply the magnitude of the temperature difference signal by the low-pass filtered mass flow signal and to produce a corresponding product signal, to subject the product signal to low-pass filtering, to detect a magnitude of the detected change of the low-pass filtered first temperature signal and to subject the signal to low-pass filtering, to divide the low-pass filtered product signal either by the low-pass filtered magnitude of the change of the low-pass filtered first temperature signal or, if the low-pass filtered magnitude is less than a predefined minimum value, by the minimum value and to produce a corresponding assessment signal, and to determine whether the thermal inertia of the catalytic converter is present or absent based on said assessment signal.

A second method comprising determining upstream and downstream emissions control device temperature changes by differentiating low-pass filtered upstream and downstream temperature measurements against time, calculating a product by multiplying a difference between the upstream and downstream temperature change signals by a low-pass filtered exhaust mass flow, and estimating an assessment of the device by low-pass filtering the product and dividing the low-pass filtered product by each of a threshold value or a low-pass filter of a magnitude of a difference between the upstream temperature change signal and an upstream temperature measurement depending on the magnitude. A first example of method further includes indicating the device as catalytically active when the assessment signal is greater than a threshold assessment signal. A second example of the method optionally including the first example further includes indicating the device as catalytically inactive when the assessment signal is less than a threshold assessment signal and adjusting engine operating parameters in response to the catalyst being inactive. A third example of the method optionally including one or more of the first and second examples further includes where the upstream and downstream temperature measurements are measured via temperature sensors upstream and downstream of the device, respectively. A fourth example of the method optionally including one or more of the first through third examples further includes where the low-pass filtered exhaust mass flow is calculated from a measured exhaust mass flow.

Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be carried out by the control system including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various actions, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described actions, operations and/or functions may graphically represent code to be programmed into non-transitory memory of the computer readable storage medium in the engine control system, where the described actions are carried out by executing the instructions in a system including the various engine hardware components in combination with the electronic controller.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure. 

1. A method for monitoring an operation of a catalytic converter disposed in an exhaust system of an internal combustion engine of a motor vehicle, wherein an exhaust gas temperature upstream of the catalytic converter and an exhaust gas temperature downstream of the catalytic converter are determined, wherein an exhaust gas mass flow through the catalytic converter is determined, wherein it is determined whether a thermal inertia of the catalytic converter is present or absent according to a presence of a triggering event taking into account the exhaust gas temperatures and the exhaust gas mass flow.
 2. The method of claim 1, wherein a temperature signal corresponding to the exhaust gas temperature upstream of the catalytic converter is determined and is then low-pass filtered, wherein a degree of change of the low-pass filtered temperature signal is detected, wherein a magnitude of the degree of change of the low-pass filtered temperature signal is detected, low-pass filtered and then compared with a predetermined limit value, and wherein the presence of the triggering event is concluded if the low-pass filtered magnitude exceeds the predetermined limit value.
 3. The method of claim 1, wherein a mass flow signal corresponding to the exhaust gas mass flow is produced and low-pass filtered, wherein the low-pass filtered mass flow signal is compared with a predetermined mass flow limit value, and wherein the presence of the triggering event is concluded if the low-pass filtered mass flow signal is less than the predetermined mass flow limit value.
 4. The method of claim 1, wherein a first temperature signal corresponding to the exhaust gas temperature upstream of the catalytic converter is produced and low-pass filtered, wherein a magnitude of a degree of change of the low-pass filtered first temperature signal is detected, wherein a second temperature signal corresponding to the exhaust gas temperature downstream of the catalytic converter is produced and low-pass filtered, wherein a change of the low-pass filtered second temperature signal is detected, wherein a mass flow signal corresponding to the exhaust gas mass flow is produced and low-pass filtered, wherein the change of the low-pass filtered second temperature signal is subtracted from the change of the low-pass filtered first temperature signal and a corresponding temperature difference signal is produced, wherein a magnitude of the temperature difference signal is detected, wherein the magnitude of the temperature difference signal is multiplied by the low-pass filtered mass flow signal and a corresponding product signal is produced, wherein the product signal is low-pass filtered, wherein a magnitude of the change of the low-pass filtered first temperature signal is detected and is low-pass filtered, wherein the low-pass filtered product signal is divided either by the low-pass filtered magnitude of the change of the low-pass filtered first temperature signal or, if the same is less than a predefined minimum value, by the minimum value and a corresponding assessment signal is produced, based on which it is determined whether the thermal inertia of the catalytic converter is present or absent.
 5. A system for monitoring an operation of a catalytic converter disposed in an exhaust system of an internal combustion engine of a motor vehicle, comprising at least one temperature sensor that is disposed upstream of the catalytic converter for detecting a first exhaust gas temperature and at least one temperature sensor that is disposed downstream of the catalytic converter for detecting a second exhaust gas temperature, characterized by at least one device for detecting an exhaust gas mass flow through the catalytic converter and at least one electronic unit that has a signaling connection to the temperature sensors and the device and that is designed to detect whether a triggering event exists or not, and to determine whether a thermal inertia of the catalytic converter is present or absent following the detection of the existence of the triggering event while taking into account the exhaust gas temperatures and the exhaust gas mass flow.
 6. The system of claim 5, wherein the electronic unit is designed to produce a temperature signal corresponding to the first exhaust gas temperature and then to subject the signal to low-pass filtering, to detect a degree of change of the low-pass filtered temperature signal, to detect a magnitude of the degree of change of the low-pass filtered temperature signal, to subject the magnitude to low-pass filtering and then to compare the low-pass filtered magnitude with a predetermined limit value, and to conclude the triggering event being present if the low-pass filtered magnitude exceeds the predetermined limit value.
 7. The system of claim 5, wherein the electronic unit produces a mass flow signal corresponding to the exhaust gas mass flow and subjects the signal to low-pass filtering, to compare the low-pass filtered mass flow signal with a predetermined mass flow limit value, and to determine the triggering event being present if the low-pass filtered mass flow signal is less than the predetermined mass flow limit value.
 8. The system of claim 5, wherein the electronic unit produces a first temperature signal corresponding to the first exhaust gas temperature and then to subject the signal to low-pass filtering, to detect a change of the low-pass filtered first temperature signal, to produce a second temperature signal corresponding to the second exhaust gas temperature and then to subject the signal to low-pass filtering, to detect a change of the low-pass filtered second temperature signal, to produce a mass flow signal corresponding to the exhaust gas mass flow and then to subject the signal to low-pass filtering, to subtract the change of the low-pass filtered second temperature signal from the change of the low-pass filtered first temperature signal and to produce a corresponding temperature difference signal, to detect a magnitude of the temperature difference signal, to multiply the magnitude of the temperature difference signal by the low-pass filtered mass flow signal and to produce a corresponding product signal, to subject the product signal to low-pass filtering, to detect a magnitude of the detected change of the low-pass filtered first temperature signal and to subject the signal to low-pass filtering, to divide the low-pass filtered product signal either by the low-pass filtered magnitude of the change of the low-pass filtered first temperature signal or, if the low-pass filtered magnitude is less than a predefined minimum value, by the minimum value and to produce a corresponding assessment signal, and to determine whether the thermal inertia of the catalytic converter is present or absent based on said assessment signal.
 9. A method comprising: determining upstream and downstream emissions control device temperature changes by differentiating low-pass filtered upstream and downstream temperature measurements against time; calculating a product by multiplying a difference between the upstream and downstream temperature change signals by a low-pass filtered exhaust mass flow; and estimating an assessment of the device by low-pass filtering the product and dividing the low-pass filtered product by each of a threshold value or a low-pass filter of a magnitude of a difference between the upstream temperature change signal and an upstream temperature measurement depending on the magnitude.
 10. The method of claim 9, further comprising indicating the device as catalytically active when the assessment signal is greater than a threshold assessment signal.
 11. The method of claim 10, further comprising indicating the device as catalytically inactive when the assessment signal is less than a threshold assessment signal and adjusting engine operating parameters in response to the catalyst being inactive.
 12. The method of claim 9, wherein the upstream and downstream temperature measurements are measured via temperature sensors upstream and downstream of the device, respectively.
 13. The method of claim 9, wherein the low-pass filtered exhaust mass flow is calculated from a measured exhaust mass flow. 